by roughing up romney on the idea he will hurt the middle class. >> he says he will cut the deficit, please. he wants $2 trillion in new defense spending that the pentagon didn't ask for. $5 trillion tax cut, future of the wealthy. >> reporter: the claim is complicated by the way biden framed the argument. >> how they can justify raising taxes in the middle class has been buried the last four years. how in lord's name can they justify raising their taxes? >> obama officials today insisted that was not a gaffe, biden clarified. >> the middle class was buried by the policies of romney and ryan supported. >> republicans like rubio are off to the races. >> those happen to be the words that the distinguished vice president of the united states mr. joe biden. no, don't boo. he is the best thing we've got going, guys. >> reporter: now denver has always been big for this president. in 2008 is where he launched the hope and change in front of the great columns of the democratic convention. 2009. this is where he signed the stimulus in law. tonight, he puts it all on the line trying to make hi